Electric Field in Material Space
Just as electric fields can exist in free space, they can exist in material media. Materials are broadly classified in terms of their electrical properties as conductors, semiconductors and insulators. Non-conducting materials are usually referred to as insulators or dielectrics.
A conductor is a material which contains movable electric charges. Metals such as copper aluminium are examples of conductors. In a Conductor the outer electrons of the atoms are loosely bound and free to move through the material. In conductors, the valence electrons are essentially free and strongly repel each other. Any external influence which moves one of them will cause a repulsion of other electrons which propagates through the conductor.
In an insulator the free electric charges are very few in number. Most solid materials are classified as insulators because they offer very large resistance to the flow of electric current. In insulators the outermost electrons are so tightly bound that there is essentially zero electron flow through them with ordinary voltages.
The properties of semiconductors lie in between conductors and insulators.
Here we examine the electric field inside a conductor and an insulator.